Sculpt Mode is similar to Edit Mode in that it is used to alter the shape of a model,
but Sculpt Mode uses a very different workflow:
instead of dealing with individual elements (vertices, edges, and faces),
an area of the model is altered using a brush.
In other words, instead of selecting a group of vertices,
Sculpt Mode manipulates geometry in the brush region of influence.

Sculpt mode is selected from the mode menu of the 3D View header.
Once sculpt mode is activated, the Tool Shelf of the 3D View will change
to sculpt mode specific panels. The panels will be Brush,
Texture, Tool, Symmetry, Stroke, Curve, Appearance, and Options.
A red circle will appear and follow the location of the cursor in the 3D View.

Here you can select the type of brush preset to use.
Reset Brush will return the settings of a brush to its defaults.
You can also set Blender to use the current brush for Vertex Paint Mode,
Weight Paint Mode, and Texture Paint Mode using the toggle buttons.